Relaying is considered for LTE-Advanced as a tool to improve, for example, the coverage of high data rates for User Equipment (UE), group mobility, temporary network deployment, the cell edge throughput and/or to provide coverage in new cell areas. The relay node is wirelessly connected to the radio-access network via a donor cell. The connection can be:                inband, in which case the network-to-relay link shares the same frequency band with direct network-to-UE links within the donor cell. Rel-8 UEs (see 3GPP specifications TS 36.211 V8.6.0, TS 36.212 V8.6.0 and TS 36.213 V8.6.0) should be able to connect to the donor cell in this case.        outband, in which case the network-to-relay link does not operate in the same frequency band as direct network-to-UE links within the donor cell.        
A Type 1 relay is an inband relay that controls cells of its own. The relay controls one or several cells and a unique physical-layer cell identity is provided in each of the cells controlled by the relay. The same RRM (Radio Resource Management) mechanisms are available and from a UE perspective there is no difference in accessing cells controlled by a relay and cells controlled by a “normal” eNodeB (LTE base station). The cells controlled by the relay should support also LTE Rel-8 (legacy) UEs.
For inband relaying, the eNodeB-to-relay link operates in the same frequency spectrum as the relay-to-UE link Due to the relay transmitter causing interference to its own receiver, simultaneous eNodeB-to-relay and relay-to-UE transmissions on the same frequency resource may not be feasible unless sufficient isolation of the outgoing and incoming signals is provided e.g. by means of specific, well separated and well isolated antenna structures. Similarly, at the relay it may not be possible to receive UE transmissions simultaneously with the relay transmitting to the eNodeB.
One possibility to handle the interference problem is to operate the relay such that the relay is not transmitting to UEs when it is supposed to receive data from the donor eNodeB, i.e. to create “gaps” in the relay-to-UE transmission. These “gaps” during which UEs (including Rel-8 UEs) are not supposed to expect any relay transmission can be created by configuring MBSFN (Multi-media Broadcast over a Single Frequency Network) sub-frames. Similarly, Relay-to-eNodeB transmissions can be facilitated by not allowing any UE-to-relay transmissions in some sub-frames. However, the use of the MBSFN sub-frame introduces some design restrictions for the relay control structure as the relay can not read the PDCCH (Physical Downlink Control Channel) of the donor cell. Hence a new control channel must be designed solely for relay stations.